Balloon catheters are commonly used, particularly the Foley catheter which finds major use in uninary tract surgery. The catheter is inserted into the urethra until the catheter head extends into the bladder. Then a balloon adjacent the head is inflated to retain the catheter for usually a period of days. However, a catheter may be inserted for an indefinite period of time in chronic situations.
The early designs of balloon catheters were made of natural rubber latex. As is known, the latex causes a reaction in the tissues which are adjacent to it, which can be quite uncomfortable for the patient, and which is medically undesirable.
In more recent times, balloon catheters have been fabricated out of silicone rubber, or out of latex which is coated with a film of silicone rubber, to avoid the tissue reaction problem. However, these catheters are considerably more expensive than the latex catheters, and they share with the latex catheters the disadvantage that they are somewhat difficult to fabricate, because both latex and silicone rubber are generally not thermoplastic materials, and thus must be cured over a period of time in order to obtain the desired physical properties.
Another type of balloon catheter has a polyvinyl chloride tubular shank, attached to a natural rubber latex balloon, because of the unsuitability of vinyl as a balloon material. Thus, the latex balloon remains as an irritant. Also, vinyl catheters have exhibited an undesirable "feel" to the patient.
In accordance with this invention, a new catheter is provided which can exhibit an extremely low toxicity so that little or no irritation is felt by the patient. The balloon of the catheter of this invention exhibits particularly good elastomeric recovery, with low creep, so that there is little "pruning" upon deflation of the balloon, i.e. the formation of wrinkles in the balloon.
While the material of the catheter of this invention, on a cost basis, is similar to natural rubber latex and the like, it is as non-toxic as silicone rubber, thereby combining the advantages of the two types of catheters.
Also, as a further advantage, the tubular shaft of the catheter of this invention may be formed by simple extrusion, without a post cure time, since the material of the catheter may be thermoplastic, but also of a softening temperature which permits autoclaving of the catheter if desired.
Also, parts of the catheter may be thermoformed or injection molded as desired. The tubing of the catheter of this invention may be kink and collapse resistant upon aspiration and normal use, and it may be fabricated by heat sealing, without separate adhesives.
Also, the cost of fabrication of the catheters of this invention may be further reduced by the fact that scrap materials from the production of the catheter may be reused in molding or extrusion, since the material is of thermoplastic rather than of the thermoset type.
The catheters of this invention are also stable under radiation sterilization.